The Aston Model 1842 single-shot percussion-based pistol was a further evolution of the earlier Aston Model 1836 flintlock. The original sidearm was completed in the typical flintlock action of the period, complete with hinged hammer, frizzen and pan, and frizzen spring arrangement designed to actuated the firing of a single lead ball from the barrel. The guns had a walnut stock secured with iron fittings and the stock formed an elegantly shaped curve acting as the grip. The action was set to the left side of the gun body. A hinged ramrod was conveniently set under the barrel.
As with other firearms of the time, the Model 1836 pistols became good candidates for modernization to the percussion system of operation in which the falling hammer actuated an ignition cap, in turn igniting powder at the breech of the weapon, the resulting forces driving the bullet out of the barrel (the action was akin to a child's toy cap gun). This method of firearms operation proved vastly more reliable than the old flintlock system which was influenced by environmental factors - percussion guns could now fire in rainy weather.
By 1842, the Aston pistols, in accordance with War Department standardization, had given up their hammer, pan-and-frizzen flintlock schemes for the more reliable percussion cap design. Brass hardware also now took the place of the original iron fittings holding the walnut stock together. The initial U.S. government contract undertaken by H. Aston covered 24,000 units from 1846 until 1851 while a further 6,000 units arrived thereafter (into 1852) under the revised H. Aston & Company name. Following this, the gun and its associated tooling was sold off to Ira N. Johnson after which another 10,000 units emerged from 1853 to 1855.
The guns were typically issued to horse-mounted infantry known as "Dragoons" - a term taken from British cavalry regiments - who could appreciate the compact form of the pistols in close-quarters combat (whether as mounted troops or unmounted foot soldiers) - the single-shot nature of the pistol proving devastatingly effective alongside the sabre at such ranges and all this behind the power of a charging horse. Dragoon elements would carry two of the guns ready-to-fire at the saddle.
Aston Model 1842 pistols were in circulation by the time of the fighting of the American Civil War (1861-1865) and some may have found their way outside of the military in the hands of private owners or militia elements.